The present invention relates to a sensor for monitoring rotation of an object about an axis. More particularly, the present invention relates to a sensor for monitoring a direction of rotation of a vehicle tire about its mounting axis.
Monitoring a condition of a vehicle tire during operation of the vehicle is becoming increasingly more popular with the use of run-flat tire technology. Tire condition monitors alert the vehicle driver when a tire condition is outside of a normal operating range. For example, if the pressure in a particular tire is low, the tire condition monitor associated with that tire can alert the driver of the low pressure condition.
The present invention relates to a sensor for monitoring rotation of an object about an axis. More particularly, the present invention relates to a sensor for monitoring a direction of rotation of a vehicle tire about its mounting axis.
Monitoring a condition of a vehicle tire during operation of the vehicle is becoming increasingly more popular with the use of run-flat tire technology. Tire condition monitors alert the vehicle driver when a tire condition is outside of a normal operating range. For example, if the pressure in a particular tire is low, the tire condition monitor associated with that tire can alert the driver of the low pressure condition.
There are many known tire condition monitoring systems. Many of the known tire condition monitoring systems have tire condition monitors that sense pressure within a tire. The tire condition monitors transmit signals indicative of either an alert condition or indicative of the actual pressure within the tire. A vehicle based controller receives the transmitted signals. Generally, each tire of the vehicle has an associated tire condition monitor. Thus, it is desirable to correlate signals received at the vehicle based controller with the particular tire condition monitor sending the signal.
Some of the known tire condition monitoring systems provide each tire condition monitor with an associated identification code. The vehicle based controller is programmed with the respective identification codes and the location on the vehicle correlating to each respective identification code. With these known systems, the vehicle based controller must be reprogrammed each time a tire condition monitor is replaced or each time the tires of the vehicle are rotated.
Other known tire condition monitoring systems wire antennas into each wheel well of the vehicle. Each wheel well antenna receives the transmitted signals from its associated tire condition monitor and transfers the signals to the vehicle based unit. Since the wheel well antennas are hard wired to the vehicle based unit, the location of a tire condition monitor providing a condition signal is known.
In accordance with an exemplary embodiment of the present invention, a sensor is provided for monitoring a direction of rotation of an object about an axis. The sensor comprises a switch member that is urged into a neutral position relative to the object and is movable relative to the object away from the neutral position. A direction of relative movement between the switch member and the object is indicative of the direction of rotation of the object. Inertia of the switch member during initial rotation of the object results in relative movement of the switch member away from the neutral position. Centrifugal force during object rotation further acts on the switch member to enhance the relative movement of the switch member away from the neutral position. The sensor further comprises a device for monitoring the direction of relative movement between the switch member and the object and for providing a signal indicative thereof.
In accordance with another exemplary embodiment of the present invention, a sensor is provided for monitoring rotation of an object about an axis. The sensor comprises a movable switch member that is urged into a neutral position and that is adapted so as to move relative to switch contacts in response to rotational acceleration of the object. The switch member is further responsive to centrifugal force resulting from object rotation so as to enhance movement of the switch member and thereby close the switch contacts. Closure of the switch contacts is indicative of the direction of rotation of the object. The sensor also comprises a device for monitoring switch closure and for providing a signal indicative thereof.
In accordance with yet another exemplary embodiment of the present invention, an apparatus is provided for sensing a condition of a vehicle tire. The apparatus comprises a tire rotation sensor for monitoring rotation of the vehicle tire about its mounting axis. The tire rotation sensor includes a movable switch member and a monitoring device. The switch member is urged into a neutral position relative to the tire and is movable relative to the tire away from the neutral position. A direction of relative movement between the switch member and the tire is indicative of the direction of rotation of the tire. Inertia of the switch member during initial rotation of the tire results in relative movement of the switch member away from the neutral position. Centrifugal force during tire rotation further acts on the switch member to enhance the relative movement of the switch member away from the neutral position. The monitoring device monitors the direction of movement of the switch member and provides a rotation direction signal indicative thereof. The apparatus further comprises a controller for receiving the rotation direction signal from the monitoring device and for providing a transmission signal indicative of the rotation direction signal. The apparatus still further comprises a transmitter for transmitting the transmission signal.